Commutator



Dec. 27, 1949 R. A. SAUER COMMUTATQR Filed Feb. 21, 1948 a a TA m5 w W fix am flrm lvars Patented Dec. 27, 1949 UNITED STATES OFF ICE COMMUTATOR Ronald A. Sailor, Cleveland, Ohio Application February' 21, 1948, Serial N 0. 1.0;05l

8 Claims. 1

This invention. relates to commutators for dynamo electric machines.

Inthese commutatorsi-t isnecessary to insulate the copper segments of. the commentators by dielectric material arranged between the segments; Mica, because of its advantageous mechanicalstrengthand insulating property, ordinarily has been used as the insulating material.

In using mica for this purpose it hasbeen found necessary to undercut the-mica by sawing slots between the adjacent copper segments of the commutator. The necessity of this procedure arises because the micais' harder than the copper segments and should: not come in contact with the brushes: oiv the commutator, particularly with. the soft carbon. brushes thereof. Ihe undercutting of the mica by providing the slots referred to removes the mica from adjacent the brush engaging surface of thecommutator. In undercutting the mica, however, care must-be takenthat none of the-mica is left in'the slots since this might result in brush wear if the brushes came in contact with the mica so left.- In addition, the mica does not wear away as fast asthe copper and hence high spots are formed.

on the commutator'causing-the brushes to jump and: resultingv in excessive sparking tending toburn the commutator.

in order to avoid the disadvantages outlined above in the use of mica as theinsulating material between the copper segments of acom-muta-- tor, recourse has been had. to the use: of a composite strip of insulating materials between the segments. formed of a strip of mica located inwardly of the periphery of the commutator and'of a strip of different dielectric material. located adjacent the periphery or brush engaging surface of the com mutator and outwardly of the strip of. mica. The strip of different dielectric material is softer and less abrasive than the copper segments and may be formed: of paper, cardboard,. press board .or any other similar or suitable material made from paper or fibrous pulp.

Hereto-iore inusing, thecomposite strips of insulating materials between the copper segments of a commutator the mica strip and" the dielectric fibrous strip of material have: simply contacted: each other along a straight edge and the retention of the fibrous strip in position between the copper segments has been effected merely by the action of the copper segments on the softer strip of fibrous material. However", it has been found in use that: this gripping action. of

the copper segments on the softer strip oifibrous The composite strip referred to is 2. material. is frequently. insumcient to hold thev strip of fibrous material properly in. position under the highcentri-iugal forces towhich the strip is subjected. in high. speed rotation. of. the commutator. It has. been found that sometimes the strip of fibrous material shifts so as to project beyond the circumference of the commutator and inextreme cases the fibrous strip has even been displaced entirely from between. the copper segments. The shifting or displacement of the fibrousstrip of materialresults in an uneven or interrupted peripheral surface on the commutator, as distinguished from the smooth peripheral surface required for proper functioning of the commutator.

An. object of. thisinventionis to provide a commutator construction wherein the copper segments are insulated from each other by composite strips of insulating material, with each composite. strip comprising an inner strip or portion of mica and an outer strip or portion of. softer fibrous insulating material, the inner and outer strips or portions of the composite strip being mechanically interlocked to each other, wherefore the composite strip in efiect functions as a single: strip andobviates all likelihood of the outer strip being displaced relative to the inner strip, which. latter strip is positively anchored in.

position between the copper segments of the commutator.

Av further object of the invention is to provide,

a commutator wherein composite insulating strips of the-type referred to in the first named object are arranged between the copper segments of the commutator and which compositestrips are so formed that the outer strips of softer fibrous material are held in position not only by the gripping action of the copper segmentsthereon. but also by a positive mechanical interlock with the inner mica strips that are positively anchored in position in the commutator.

A further and general object of the invention is to provide a commutator construction employ-mg composite insulating stripsbetween the 3 of an embodiment of the invention which is to follow.

Referring to the accompanying drawing illustrating said embodiment of the invention,

Fig. 1 is a perspective view of a commutator utilizing the invention therein.

Fig. 2 is a part elevational and part longitudinal sectional view of the commutator shown in Fig. l, the section being taken to show in elevation one of the composite insulating strips which are located between the copper segments of the commutator.

Fig. 3 is a detached elevational view of the composite insulating strip.

Fig. 4 is an end elevational view of the insulating strip shown in Fig. 3.

Fig. 5 is a detached perspective view of the outer portion or strip of the composite insulating strip shown in Figs. 2, 3 and 4 and Fig. 6 is a detached perspective view of the inner portion or strip of the composite insulating strip shown in Figs. 2, 3 and 4.

The commutator to which the present invention relates comprises a circular series of radially extending copper segments In which are insulated from each other by insulating strips located between the copper segments. The opposite ends of the copper segments are machined to provide recesses or notches which receive clamping members II, it being understood thatthe clamping members II also extend into similar notches formed in the opposite ends of the insulating strips.

One of the clamping members I I, the left hand one as viewed in Fig. 2, may be formed integral with a sleeve l2 extending through the commutator and provided at one end which is adjacent said one clamping member with an extension I3. The other clamping member H, the right hand clamping member as viewed in Fig. 2, is mounted on the sleeve I2 and as shown may be held in assembled position on the sleeve and in clamping engagement with the insulating strips and copper segments by means of a clamping flange I4 formed on the sleeve I2. If desired, the other clamping member II may be assembled and held on the sleeve I2 by means of a holding nut or element havin threaded engagement with the sleeve I2. The sleeve I2 and its extension I3 functions as the means for attaching the commutator to a shaft not shown.

Suitable insulation I5 and I6 is arranged between the copper segments, the insulating strips, the clamping members II and the sleeve I2. The detailed description thus far set forth de-- scribes a commutator construction which is well known in the art and therefore a more specific explanation of this known commutator construction will not be necessary for an understanding of the present invention by one skilled in this art.

The present invention contemplates a commutator employing as insulation between the copper segments I 0 thereof composite insulating strips each formed of an inner portion or strip I! and an outer portion or strip I8. The outer strip or portion I8 of each composite insulating strip is provided adjacent its opposite ends with recesses I9 which when the outer portion or strip I8 is assembled to the inner strip or portion I! cooperate with recesses 20 formed in the opposite ends of the inner strip or portion H to provide in the composite strip the notches which receive the clamping members H. The manner in which the recesses I9 and 2|] cooperate to provide the notches that receive the clamping members II is clearly indicated in Fig. 3. Reference to Fig. 2 will indicate that the clamping members II positively anchor the inner strip or portion I! in position between the commutator segments since the clamping members II overlie the recesses 20 of the irmer portion or strip II. Therefore when the commutator is completely assembled the inner portions I! of the composite insulating strips will be positively locked in position by the clamping members II and also will be firmly gripped by the copper segments between which the inner portions or strips ll of the composite strips are located.

As already stated, the composite insulating strips previously used in commutators have the inner portions of the strips formed of mica, due to the mechanical strength and insulating property of this material. Also, as stated, the outer portions of such composite insulating strips have been formed of fibrous, relatively soft dielectric material such as paper, cardboard, press board or other suitable material of this type.

The composite insulating strips of the present invention follow the usual practice to the extent that the inner portions I'I thereof are formed of mica while the outer portions I6 thereof are formed of a fibrous material such as just above referred to. However, the present invention departs from the previous practice in that the outer portions I8 of the composite strips are mechanically interlocked with the inner portions I! and hence the retention of the outer portions IB a ainst shifting or displacement under the centrifugal forces is not dependent alone on the gripping action of the segments on the outer portions.

The mechanical interlock between the inner and. outer portions of the composite insulating strips may take various forms, one of which is illustrated herein. It will be noted that the inner portion I1 is provided with a dovetail tongue 2| while the outer portion I8 is provided with a complementary recess 22 receiving the tongue 2 i, wherefore the inner portion I1 and the outer portion I8 are mechanically and positively interconnected by a dovetail connection. Consequently since the inner portion I1 is positively clamped in position by the commutator segments and the clamping members II, and the outer portion I8 is positively and mechanically interconnected to the inner portion ll such outer portion I8 is positively held against displacement due to centrifugal forces.

The upper edge, as viewed in the drawing of the inner portion ll of the composite insulating strip, is provided on each side of the dovetail tongue 2I with straight portions 23 that extend parallel to the axis of the sleeve I2 and firmly engage with straight surfaces 24 formed on the lower edge of the outer portion I8 on opposite sides of the recess 22. It will be seen that when the inner and outer portions I! and GS of the composite insulating strip are mechanically interconnected as shown in Figs. 2 and 3, the composite strip forms an uninterrupted insulating layer of material intermediate the copper segments.

From the foregoing description it will be noted that the composite insulating strips embodying the present invention not only have the advantages of the previously used composite insulating strips wherein the inner and outer portions of the strips are not positively and mechanically interlocked but also avoid the disadvantages inherent in the use of such previous composite insulating strips, all as referred to hereinbefore.

Although a preferred embodiment of the invention has been illustrated and described herein it will be understood that the invention is susceptible of various modifications and adaptations within the scope of the appended claims.

Having thus described my invention, I claim:

1. A commutator comprising a circular series of copper segments, preformed composite insulating strips arranged between adjacent segments, means for clamping the segments together whereby the insulating strips are clamped between the segments, said composite insulating strips each being in two portions, the outer portion adjacent the brush engaging surface of the segments being formed of a material less abrasive than the segments while the inner portion is formed of a different material, said inner and outer portions of the composite strips being provided with cooperating m ans mechanically and positively interlocking said outer and inner portions.

2. A commutator comprising a circular series of copper segments, composite insulating strips arranged between adjacent segments, said composite insulating strips being in two portions with the outer portion adjacent the brush engaging surface of the segments being formed of material less abrasive than the segments while the inner portion is formed of a different material, and means for clamping the segments together whereby the insulating strips are clamped between the segments, said means including means for positively locking the inner portion of the insulating strips against movement under centrifugal force, said inner and outer portions of the insulating strips having cooperating means mechanically and positively interlocking the out-- or portion with the inner portion.

3. A commutator as defined in claim 1 and wherein the cooperating means on the inner and outer portions of the insulating strips consists of interengaging tongues and grooves formed on said inner and outer portions of the insulating strips.

4. A commutator as defined in claim 1 and wherein the cooperating means which mechanically and positively interlock the inner and outer portions of the insulating strips comprises tongues on the inner portions and cooperating grooves on the outer portions.

5. A commutator as defined in claim 1 and wherein the cooperating means which interlocks the inner and outer portions of the insulating strips comprises a dovetail connection between said inner and outer portions.

6. A commutator as defined in claim 2 and wherein the cooperating means on the inner and outer portions of the insulating strips consists oi interengaging tongues and grooves formed on said inner and outer portions of the insulating strips.

'7. A commutator as defined in claim 2 and wherein the cooperating means which mechanically and positively interlock the inner and outer portions of the insulating strips comprises tongues on the inner portions and cooperating rooves on the outer portions.

8. A commutator as defined in claim 2 and wherein the cooperating means which interlocks the inner and outer portions of the insulating strips comprises a dovetail connection between said inner and outer portions.

RONALD A. SAUER.

REFERENfiES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 854,781 Underwood May 28, 1907 2,141,268 Dunbar Dec. 27, 1938 FQREIGN PATENTS Number Country Date 298,288 Germany June 15, 1917 

